Among doctors who write with acuity and grace, Sacks (The Man Who Mistook His Wife for a Hat) takes a higher place with each successive book. In this provocative collection of previously published essays, the noted neurologist describes his meetings with seven people whose ``abnormalities'' in brain function generate new perspectives on the workings of that organ, the nature of experience and concepts of personality and consciousness. ``It's not gentle,'' notes Canadian surgeon Carl Bennett of Tourette's syndrome; Bennett's compulsive lungings, tics and speech patterns are stilled when he is in the operating room and moderated, Sacks observes firsthand from the passenger seat, while Bennett is flying his Cessna Cardinal. The broad effects and differing degrees of autism are probed in his conversations and observations, over many years, with Stephen Wiltshire, an autistic British artist-prodigy, and his visit with Temple Grandin, an animal behavior specialist. Writing with eloquent particularity and compassionate respect, Sacks enlarges our view of the nature of human experience. Illustrations. 100,000 first printing; BOMC selection; author tour; Random House AudioBook (ISBN 0-679-43956-0, $17). (Feb.)